Vapor deposition apparatus

ABSTRACT

A vacuum chamber contains a crucible of coating material disposed below the path of a moving substrate to be coated. A plurality of electron guns directs energy toward a first predetermined area on the surface of said material whereby the material within said area is vaporized. The crucible is then moved whereby said energy is directed toward a second predetermined area on the surface of said material while said first area is disposed so as to receive additions of the coating material from a plurality of material supply means disposed above said crucible.

I United States Patent 1 13,575,132

[72] inventors Herbert H. Francisco; 3,364,296 1/1968 Smith, Jr. 13/31 Anthony P. Martocci, Bethlehem, Pa. 3,432,335 3/1969 Schiller et a1.. 1 18/49.1X [2]] Appl. No. 770,503 3,437,734 4/1969 Roman et a1... 13/31 [22} Filed Oct. 25, 1968 3,467,058 9/1969 Box et al 13/31X [45] Patented Apr. 13, 1971 FOREIGN PATENTS [731 Assgnee 882,171 7/1953 Germany 1 18/495 Primary Examiner-Morris Kaplan At[grney joseph OKeefe 1 Claim, 3 Drawing Figs. [52] US. Cl 118/495,

219/ 121 [5 lnt. A vacuum chamber contains a rucible of oat- [50] Field of Search 1 18/48- ing materia| disposed below the path f a moving Substrate to 13/ 3 2 1 9/273, 12 be coated. A plurality of electron guns directs energy toward a q l 335 first predetermined area on the surface of said material whereby the material within said area is vaporized. The cruci- [56] References Cited ble is then moved whereby said energy is directed toward a UNITED STATES PATENTS second predetermined area on the surface of said material 3,263,648 8/ 1966 Chapman et a1 1 18/491 while said first area is disposed so as to receive additions of the 3,271,179 9/1966 Smith, Jr. 118/49.1X coating material from a plurality of material supply means 1 18/49. 1 X disposed above said crucible.

3,303,320 2/1967 Muller Patented April 13, 1971 I 3,575,132

3 Sheets-She eti l/crberf b. Franc/3w inf/7027 R/Wor/occi Patented April 13, 1971 5 Sheets-Sheet 5 VAPOR DEPOSITION APPARATUS BACKGROUND OF THE INVENTION This invention relates to an apparatus for coating articles with vapor-deposited materials, and more particularly to a method and apparatus for replenishing coating material which has been vaporized.

The coating material is usually placed in a crucible disposed beneath the article to be coated. In a continuous operation, e.g. the coating of a moving steel strip, coating material must be added during the operation to replace the material which has vaporized. 1

Electron beams are frequently used for vaporizing the coating material. Such beams impinge upon a predetermined area on the surface of said material, and substantially all of the metal vaporized lies within said area.

In the vacuum vapor deposition of chromium, for example, the chromium may be charged into the crucible in the form of granules or flakes. Those granules of chromium which lie within the impact area of the electron beam appear to sublime, while those granules along the periphery of said area partially melt and fuse together. As a result of this fusion, granules adjacent to the electron beam impact area do not fall into said area to replenish the material vaporized.

In the past, the discharge chutes of coating material feeders have been positioned to discharge the feed material substantially directly over the electron beam impact area. However, this method of replenishing vaporized material has been unsatisfactory, as the heat from the impact area causes the added material to splatter on the article being coated. This splattering is primarily a result of the rapid expansion of any gases in or on the added material. In addition to the foregoing, granules of material in the discharge chute tend to fuse together and thus fail to fall out of the chute and into the crucible when the feeder is actuated, e.g. vibrated.

It is an object of this invention to provide an apparatus for replenishing vaporized coating material without splattering of the article being coated and/or fusing of the material in the feeder.

SUMMARY OF THE INVENTION We have discovered that the foregoing object can be attained by spacing the feeder chute from the electron beam impact area and by moving the crucible relative to the chute and the electron gun whereby the electron beam impinges upon a different area while the chute is disposed so as to discharge feed material directly above the depleted area.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic plan view of the apparatus of the invention.

FIG. 2 is a sectional view taken along the lines 2-2 of FIG. I.

FIG. 3 is a sectional view taken along the lines 3-3 of FIG. I.

FIG. 4 is a diagrammatic plan view of an alternate form of the apparatus of the invention.

FIG. 5 is a sectional view taken along the lines 5-5 of FIG. 4.

FIG. 6 is a sectional view taken along the lines 66 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT As is shown in FIGS. 1-3, a crucible 10 containing coating material, e.g. granules of chromium I2, is disposed beneath a moving substrate, e.g. steel strip 14. Said crucible is of rectangular cross section, and is secured to a base plate 16 supported on rollers 18 rotatably mounted on the top plate 20 of a carriage 22. Secured to one end of the base plate 16 is a bracket 24 to which the piston rod 26 of a hydraulic cylinder 27 is connected, the cylinder being secured to the plate 20 by bracket 28. The carriage 22 is provided with pairs of sideplates 30 and 31, one of the plates 30 having an opening 32 through which sald piston rod 26 passes. The sideplates 30 and 31 are supported on a base 34 provided with wheels 36.

Positioned along opposite sides of the crucible I0 is a plurality of energy supply means, e.g. electron guns 38. Each electron gun 38 is disposed beneath the top plate 20 between magnetic pole pieces 40 mounted on the base 34. The pole pieces 40 control the direction of the electron beam whereby the area 42 upon which it impinges may be controlled.

A plurality of material supply means, e.g. vibrating feeders (not shown), provided with chutes 44, is arranged along opposite sides of the crucible I0. Each chute is disposed above and to the side of one of the impact areas 42. As is shown in FIG. 1, the number of chutes 44 along each side of the crucible l0 exceeds the number of electron guns 38 by one.

The subject apparatus, which is disposed in a vacuum chamber (not shown), operates as follows. The strip 14 is passed above the crucible l0 and the electron guns 38 are energized whereby energy impinges upon first predetermined areas 42 on the surface of the chromium. The hydraulic cylinder 27 is then actuated to extend the piston rod 26 whereby the crucible I0 is moved slowly to the position shown in dotted lines in FIGS. 1 and 2. As is clear, during movement of said crucible the electron beams impinge on second, predetermined areas on the surface of the chromium 12. When the depleted areas in the crucible 10 are disposed beneath the feeder chutes 44, the feeders are vibrated whereby chromium granules fall into said depleted areas.

The rate at which the crucible 10 is moved must be sufficiently slow so that the electron beam can heat the coating material to a vaporization temperature, yet fast enough to prevent said beam from penetrating excessively into said material. The exact speed is dependent upon the properties of the coating material, the power density in the impact area, the desired depth of penetration and the distance across the impact area in the direction of crucible movement. For example, if the coating material is chromium granules, we have found a speed of 60 linear inches per hour is satisfactory for a power density of 7 kilowatts per square inch and a depth of penetration of 1 inch, the distance across the impact area 42 in the direction of crucible movement being about I inch.

Considering only the impact areas at the far left of FIG. 1, it can be seen that the original areas 42, i.e., the impact areas before movement of the crucible 10 to the position shown in dotted lines is initiated, are disposed in the positions indicated in dotted lines as 42a after said movement. These areas 42a are directly under the feeder chutes 44 to the far left in FIG. I, and these areas, as well as the depleted areas extending to the right thereof to the edge of the new impact areas, are replenished with coating material by vibrating the feeders provided with said chutes. When the crucible 10 is returned to its original position, i.e., the position shown in solid lines, the depleted impact areas are disposedin the positions indicated in dotted lines as 42b. These areas 42b are directly under the feeder chutes 44 second from the left, and these areas, as well as the depleted areas immediately to the'left thereof, are replenished with coating material by vibrating the feeders provided with these chutes.

While FIGS. 1-3 show only means for reciprocating the crucible I0 perpendicular to the direction of strip travel, it may be desirable to provide means for imparting additional movement to the crucible in the same direction as the strip travels, thereby producing an orbital movement of the crucible.

FIGS. 4-6 show an alternate form of the apparatus of the invention. A crucible 46 of circular cross section is disposed beneath a moving strip 48 and contains a supply of coating material 50. The crucible 46 is fastened to a base plate 52 secured to the shaft 54 of a motor 56. The motor 56 is disposed in a supporting structure comprising a base plate 58, sideplates 60, and a top plate 62. The shaft 54 is provided with bearings 64.

Disposed beneath the crucible 46 on opposite sides thereof are electron guns 66 provided with pole pieces 68. The electronbeams from said guns 66 impinge upon areas 70 on the surface of the material 50. Vibrating feeders are disposed with their chutes 72 above the crucible 46 on opposite sides thereof, each chute 72 being spaced 90 from an electron gun The crucible 46 is rotated slowly during the coating operation whereby depleted areas 74 progressively pass under the chutes 72 which supply coating material 76 thereto. The exact speed of rotation is dependent upon the same factors mentioned above in connection with the reciprocating crucible shown in FIGS. 1-3.

While the invention has been described in connection with solid granules of coating material, it is also useful when the coating material is in the liquid state. Intermittent or continuous movement of the crucible prevents additions of the coating material from causing freezing of the bath in the area where the additions are made. In addition, splattering is prevented by reason of the spacing of the feeder chutes from the beam impact area.

We claim:

1. An apparatus for coating a moving substrate with vapordeposited material, comprising:

a, a vacuum chamber;

b. means, comprising a crucible of substantially rectangular cross section, for containing a supply of said material;

c. means for passing a substrate above said crucible whereby vapor emanating from said crucible may impinge upon said substrate;

d. a plurality of energy supply means arranged along opposite sides of said crucible, each of said means being adapted to direct energy toward a portion of a first predetermined area on the surface of said material whereby the material within said area is vaporized, the energy supply means located along one side being arranged in staggered relationship with respect to the energy supply means located along the opposite side;

e. a plurality of material supply means arranged along opposite sides of said crucible, each of said means being adapted to supply additions of said material to said crucible at a second predetermined area spaced from each portion of said first predetermined area toward which said energy is directed, each material supply means being disposed next to one of said energy supply means and in general alignment with a second of said energy supply means located on the opposite side of the crucible; and

. means for reciprocating said crucible relative to means (d) and (e) whereby each of said energy supply means is adapted to direct energy toward the second predetermined area on the surface of said material while said first predetermined area is disposed so as to receive additions of material from means (e). 

1. An apparatus for coating a moving substrate with vapordeposited material, comprising: a. a vacuum chamber; b. means, comprising a crucible of substantially rectangular cross section, for containing a supply of said material; c. means for passing a substrate above said crucible whereby vapor emanating from said crucible may impinge upon said substrate; d. a plurality of energy supply means arranged along opposite sides of said crucible, each of said means being adapted to direct energy toward a portion of a first predetermined area on the surface of said material whereby the material within said area is vaporized, the energy supply means located along one side being arranged in staggered relationship with respect to the energy supply means located along the opposite side; e. a plurality of material supply means arranged along opposite sides of said crucible, each of said means being adapted to supply additions of said material to said crucible at a second predetermined area spaced from each portion of said first predetermined area toward which said energy is directed, each material supply means being disposed next to one of said energy supply means and in general alignment with a second of said energy supply means located on the opposite side of the crucible; and f. means for reciprocating said crucible relative to means (d) and (e) whereby each of said energy supply means is adapted to direct energy toward the second predetermined area on the surface of said material while said first predetermined area is disposed so as to receive additions of material from means (e). 